I am pretty young and it seems stupid to me too, this guy wanted to be a React Dev. If he was ever at work writing a binary search tree by hand, or writing his own quick sort function, then he would be wasting his time and creating a huge potential problem point in the code.
This guy claims to have worked ~6 days a week for 3 months not to become a great full stack dev, but to become a great interviewee. Seems kinda backwards to me.
This is what drives me crazy. I'm a bootcamp grad, and I've been interviewing for 6 months. I've spent EVERY single day of those six months, (besides applying and networking and interviewing), working on coding, design, projects, and leveling up so I can collaborate with a team. This guy spends all of his time working on stuff that is considered "level 2", and he will make double what I end up getting. Frustrating.
As a former bootcamp grad, please prioritize interviewing skills over development skills. once you get a good job, you can spend your free time on side projects but until then you need to practice on interviews not coding.
Sadly it's the reality of interviewing and I hate it but there is nothing you can do until you are an experienced dev and can leverage your power to say "I refuse to work or interview at companies with dumb interviewing processes."
Play the game. You know the rules and you know what you need to do to win the game. So just suck it up and do it. It does not take much more than 1-2 hours of dedicated interview prep over the course of a month to be successful in whiteboard style interviews.
I have seen that for internal promotions too on guy I knew spent months working his promotion my boss wryly commented of course he has not done any real work for 6 months.
This guy claims to have worked ~6 days a week for 3 months not to become a great full stack dev, but to become a great interviewee. Seems kinda backwards to me.